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author | Ben Gamari <bgamari.foss@gmail.com> | 2016-12-15 18:57:26 -0500 |
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committer | Ben Gamari <ben@smart-cactus.org> | 2016-12-15 18:57:53 -0500 |
commit | 0d213c18b6962bb65e2b3035a258dd3f5bf454dd (patch) | |
tree | 6bb856c068bfb7c82584f913701f8d8081ae8482 | |
parent | cd4b202f24da928adf66c05443b457002ab6a3e1 (diff) | |
download | haskell-0d213c18b6962bb65e2b3035a258dd3f5bf454dd.tar.gz |
UniqSupply: Use full range of machine word
Currently uniques are 32-bits wide. 8 of these bits are for the unique
class, leaving only 24 for the unique number itself. This seems
dangerously small for a large project. Let's use the full range of the
native machine word.
We also add (now largely unnecessary) overflow check to ensure that the
unique number doesn't overflow.
Test Plan: Validate
Reviewers: simonmar, austin, niteria
Reviewed By: niteria
Subscribers: mpickering, thomie
Differential Revision: https://phabricator.haskell.org/D2844
GHC Trac Issues: #12944
-rw-r--r-- | compiler/Unique.h | 3 | ||||
-rw-r--r-- | compiler/basicTypes/UniqSupply.hs | 6 | ||||
-rw-r--r-- | compiler/basicTypes/Unique.hs | 15 | ||||
-rw-r--r-- | compiler/cbits/genSym.c | 25 |
4 files changed, 39 insertions, 10 deletions
diff --git a/compiler/Unique.h b/compiler/Unique.h new file mode 100644 index 0000000000..a786d8ff3e --- /dev/null +++ b/compiler/Unique.h @@ -0,0 +1,3 @@ +#include "../includes/MachDeps.h" + +#define UNIQUE_BITS (WORD_SIZE_IN_BITS - 8) diff --git a/compiler/basicTypes/UniqSupply.hs b/compiler/basicTypes/UniqSupply.hs index 9f97d49045..431c96cf58 100644 --- a/compiler/basicTypes/UniqSupply.hs +++ b/compiler/basicTypes/UniqSupply.hs @@ -3,7 +3,7 @@ (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 -} -{-# LANGUAGE UnboxedTuples #-} +{-# LANGUAGE CPP, UnboxedTuples #-} module UniqSupply ( -- * Main data type @@ -38,6 +38,8 @@ import Control.Monad import Data.Bits import Data.Char +#include "Unique.h" + {- ************************************************************************ * * @@ -75,7 +77,7 @@ takeUniqFromSupply :: UniqSupply -> (Unique, UniqSupply) -- ^ Obtain the 'Unique' from this particular 'UniqSupply', and a new supply mkSplitUniqSupply c - = case ord c `shiftL` 24 of + = case ord c `shiftL` UNIQUE_BITS of mask -> let -- here comes THE MAGIC: diff --git a/compiler/basicTypes/Unique.hs b/compiler/basicTypes/Unique.hs index e24d56b8c7..a6ac670407 100644 --- a/compiler/basicTypes/Unique.hs +++ b/compiler/basicTypes/Unique.hs @@ -8,6 +8,7 @@ comparison key in the compiler. If there is any single operation that needs to be fast, it is @Unique@ + comparison. Unsurprisingly, there is quite a bit of huff-and-puff directed to that end. @@ -63,6 +64,7 @@ module Unique ( ) where #include "HsVersions.h" +#include "Unique.h" import BasicTypes import FastString @@ -126,6 +128,11 @@ deriveUnique (MkUnique i) delta = mkUnique 'X' (i + delta) -- newTagUnique changes the "domain" of a unique to a different char newTagUnique u c = mkUnique c i where (_,i) = unpkUnique u +-- | How many bits are devoted to the unique index (as opposed to the class +-- character). +uniqueMask :: Int +uniqueMask = (1 `shiftL` UNIQUE_BITS) - 1 + -- pop the Char in the top 8 bits of the Unique(Supply) -- No 64-bit bugs here, as long as we have at least 32 bits. --JSM @@ -138,15 +145,15 @@ mkUnique :: Char -> Int -> Unique -- Builds a unique from pieces mkUnique c i = MkUnique (tag .|. bits) where - tag = ord c `shiftL` 24 - bits = i .&. 16777215 {-``0x00ffffff''-} + tag = ord c `shiftL` UNIQUE_BITS + bits = i .&. uniqueMask unpkUnique (MkUnique u) = let -- as long as the Char may have its eighth bit set, we -- really do need the logical right-shift here! - tag = chr (u `shiftR` 24) - i = u .&. 16777215 {-``0x00ffffff''-} + tag = chr (u `shiftR` UNIQUE_BITS) + i = u .&. uniqueMask in (tag, i) diff --git a/compiler/cbits/genSym.c b/compiler/cbits/genSym.c index 70ea417c4b..725a310253 100644 --- a/compiler/cbits/genSym.c +++ b/compiler/cbits/genSym.c @@ -1,18 +1,35 @@ - +#include <assert.h> #include "Rts.h" +#include "Unique.h" static HsInt GenSymCounter = 0; static HsInt GenSymInc = 1; +#define UNIQUE_MASK ((1ULL << UNIQUE_BITS) - 1) + +STATIC_INLINE void checkUniqueRange(HsInt u STG_UNUSED) { +#if DEBUG + // Uh oh! We will overflow next time a unique is requested. + assert(h != UNIQUE_MASK); +#endif +} + HsInt genSym(void) { #if defined(THREADED_RTS) if (n_capabilities == 1) { - return GenSymCounter = (GenSymCounter + GenSymInc) & 0xFFFFFF; + GenSymCounter = (GenSymCounter + GenSymInc) & UNIQUE_MASK; + checkUniqueRange(GenSymCounter); + return GenSymCounter; } else { - return atomic_inc((StgWord *)&GenSymCounter, GenSymInc) & 0xFFFFFF; + HsInt n = atomic_inc((StgWord *)&GenSymCounter, GenSymInc) + & UNIQUE_MASK; + checkUniqueRange(n); + return n; } #else - return GenSymCounter = (GenSymCounter + GenSymInc) & 0xFFFFFF; + GenSymCounter = (GenSymCounter + GenSymInc) & UNIQUE_MASK; + checkUniqueRange(GenSymCounter); + return GenSymCounter; #endif } |